A shooting at a rave in Aarau, Switzerland, early Sunday left one 22-year-old woman dead and five others injured.

The victims, four men and one woman between the ages of 24 and 27, were taken to hospitals with injuries ranging from minor to severe.

The shooting occurred around 2:30 a.m. at a horse-racing track where the “Aarau Rave VOL. 7” techno event was being held.

Swiss police launched a major manhunt for the attacker or attackers, with authorities saying the motive and exact circumstances remain unclear, the AP has reported.

Police have asked witnesses to provide photos or videos from the event as investigators work to determine what led to the shooting.